Method for producing surface acoustic wave resonator
By forming interlaced layers, piezoelectric layers and conductive layers on the YAG layer of the SAW resonator device, the problems of high cost and manufacturing complexity of traditional SAW resonator devices are solved, and high performance and low cost production effects are achieved.
Patent Information
- Application Number
- CN202280098659.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2022-08-05
- Publication Date
- 2025-03-11
AI Technical Summary
Traditional SAW resonator equipment has high cost and manufacturing complexity problems in the production process, making it difficult to meet the needs of high performance and low cost.
High-performance SAW resonator equipment is manufactured by forming interleaved layers, piezoelectric layers and conductive layers on the basis of the yttrium aluminum garnet (YAG) layer. This method relies on standard manufacturing techniques in the semiconductor and microelectromechanical systems (MEMS) industries, reducing production costs and simplifying the manufacturing process.
Achieve high Q-factor SAW resonator production, reducing manufacturing complexity and production costs, while meeting the needs of high performance and low power consumption.
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Figure CN119605079A_ABST
Abstract
Description
Technical Field
[0001] Embodiments of the present invention relate to a method for producing a surface acoustic wave resonator device. Background Art
[0002] A surface acoustic wave (SAW) resonator device is a resonator device that converts electrical signals into acoustic waves in a piezoelectric layer. SAW resonator devices are components used for signal processing, frequency generation, filtering, sensing applications, etc.
[0003] Wireless communication devices rely heavily on high-performance bandpass transmission filters, which are used to reject any useless input RF signals and retain only the useful transmission signals. In some wireless communication applications, the bandpass transmission filter is required to have very good selectivity for the input signal, that is, only a very narrow input spectrum band is allowed to pass. Some technical requirements for this type of filter include: high frequency; high selectivity to suppress spurious signals; large bandwidth for high data rates; low insertion loss factor for low power consumption; and miniature packaging or integrated filter modules for small handheld devices.
[0004] SAW-based frequency filters are used in most existing mobile phone systems. To reduce the inherently high insertion loss of conventional SAW resonator devices, a variety of specialized low-loss technologies have been developed, each optimized for a specific application. Summary of the invention
[0005] The purpose of the embodiments of the present invention is to provide a solution that can reduce or solve the shortcomings and problems of traditional solutions.
[0006] Another object of embodiments of the present invention is to provide a solution for producing high performance SAW resonator devices at low cost.
[0007] The above objects and other objects are achieved by the subject matter claimed in the independent claims. Further embodiments of the invention are provided in the dependent claims.
[0008] According to a first aspect of the present invention, the above objects and other objects are achieved by a method for producing a surface acoustic wave (SAW) resonator device, the method comprising:
[0009] Obtaining a yttrium aluminum garnet (YAG) layer;
[0010] forming a staggered layer on a top surface of the YAG layer;
[0011] forming a piezoelectric layer on a top surface of the staggered layer;
[0012] A conductive layer is applied on the top surface of the piezoelectric layer to form an interdigital transducer (IDT) on the top surface of the piezoelectric layer, wherein the IDT includes a first conductive electrode connected to a first bus bar and a second conductive electrode connected to a second bus bar.
[0013] The advantage of the method for producing a SAW resonator device according to the first aspect is that the method can rely on standard manufacturing techniques used in the semiconductor and micro-electromechanical systems (MEMS) industries. The most advanced layered SAW resonator devices use high resistivity silicon as a high phase velocity layer in their structure, which is expensive to produce. In addition, no complex "trap-rich" (TR) layer, such as polysilicon, is required at the interface with the staggered layer. This significantly reduces manufacturing complexity and reduces production costs.
[0014] In an implementation of the method for producing a SAW resonator device according to the first aspect, the phase velocity of the YAG layer is higher than the phase velocity of the piezoelectric layer.
[0015] The advantage of this implementation is that a high Q factor SAW resonator can be produced due to the waveguide effect, that is, either the substrate itself is a low loss YAG substrate, or the YAG layer prevents acoustic losses from the resonator region (i.e. from the piezoelectric layer) into the high phase velocity YAG layer.
[0016] In an implementation of the method for producing a SAW resonator device according to the first aspect, the piezoelectric layer is any one of the following: a lithium tantalate (LT) layer, a lithium niobate (LN) layer, and an aluminum nitride (AlN) layer.
[0017] The advantage of this implementation is that these materials are either widely available on the market in wafer form with various diameters and cut angles, such as LT and LN, or can be deposited by some mature technologies, such as AlN.
[0018] In an implementation of the method for producing a SAW resonator device according to the first aspect, the interleaved layers include silicon oxide layers.
[0019] The silicon oxide layer can be configured according to the temperature compensation requirements of the SAW resonator device.
[0020] An advantage of this implementation is that the staggered layers can be used as wafer bonding layers between layers above the YAG layer and between the YAG layers.
[0021] In an implementation of the method for producing a SAW resonator device according to the first aspect, the conductive layer comprises any one of the following: an aluminum layer, an aluminum-copper alloy layer, a copper layer, a copper-aluminum alloy layer, a chromium layer, a titanium layer, a tungsten layer, a gold layer, a palladium layer and a molybdenum layer.
[0022] In an implementation of the method for producing a SAW resonator device according to the first aspect, the method comprises: before applying the conductive layer on the top surface of the piezoelectric layer,
[0023] Laying a high-speed dielectric layer on the top surface of the piezoelectric layer;
[0024] An opening is created in the high speed dielectric layer to form the IDT on the top surface of the piezoelectric layer.
[0025] In an implementation of the method for producing a SAW resonator device according to the first aspect, the high-speed dielectric layer comprises any one of the following: silicon nitride, aluminum oxide, aluminum nitride and beryllium oxide.
[0026] In one implementation of the method for producing a SAW resonator device according to the first aspect, the method comprises:
[0027] forming a dielectric layer on the top surface of the conductive layer and / or the top surface of the piezoelectric layer; or
[0028] A dielectric layer is formed on a top surface of the high-speed dielectric layer.
[0029] The advantage of this implementation is that the conductor pattern and the piezoelectric layer can be protected from subsequent production steps such as packaging and assembly, and the dielectric layer itself can be used to adjust the resonant frequency of the SAW resonator device and thus improve the yield.
[0030] In an implementation of the method for producing a SAW resonator device according to the first aspect, the dielectric layer comprises any one of the following: silicon nitride and silicon oxide.
[0031] In an implementation of the method for producing a SAW resonator device according to the first aspect, the YAG layer is a YAG thin film layer, and the method includes:
[0032] The YAG layer is formed on the top surface of the substrate.
[0033] The advantage of this implementation is that it may be possible to reduce production costs because no YAG substrate needs to be manufactured. In addition, the diameter of the layered SAW wafer stack is no longer limited by the production size limitations of the YAG crystal boule. The use of YAG thin layers can also improve the thermal performance of the SAW resonator device.
[0034] In an implementation of the method for producing a SAW resonator device according to the first aspect, the thickness of the YAG layer is in the range of 1 to 3 times the spacing between the conductive electrodes of the IDT.
[0035] The advantage of this implementation is that the acoustic waves can be effectively confined to the layers above the YAG layer to achieve the desired waveguide effect.
[0036] In an implementation of the method for producing a SAW resonator device according to the first aspect, the spacing defines a resonant frequency of the SAW resonator device and the spacing depends on a phase velocity of a main mode of a surface acoustic wave propagating in the piezoelectric layer during operation.
[0037] In an implementation of the method for producing a SAW resonator device according to the first aspect, the substrate comprises any one of the following: fused silica, quartz and silicon.
[0038] The advantage of this implementation is that wafers made of these materials are widely available in the market, are inexpensive, have good thermal conductivity and coefficient of thermal-expansion (CTE) properties, and provide solid mechanical support for the entire structure of the SAW resonator device.
[0039] In an implementation of the method for producing a SAW resonator device according to the first aspect, obtaining the YAG layer comprises:
[0040] Growing YAG crystals;
[0041] The YAG crystal is wafered to form the YAG layer.
[0042] The advantage of this implementation is that a single-crystal substrate with a small number of defects in the structure can be obtained, which ensures that the material has the highest Q factor, thermal conductivity and Young's modulus.
[0043] In an implementation of the method for producing a SAW resonator device according to the first aspect, the YAG layer has any one of the following: <111> Crystal orientation, <100> Crystal orientation, <110> Crystal orientation or polycrystalline structure.
[0044] The advantage of this implementation is that it has <111> Oriented crystals have the least number of defects associated with their growth (production) mechanism. <100> and <110> The crystals have a central core, i.e. a defect channel formed due to the crystal faceting. In addition, secondary cores may also appear at the edges along the (100) and (010) axes. This effectively compromises the desired material properties.
[0045] In an implementation of the method for producing a SAW resonator device according to the first aspect, the root mean square (RMS) surface roughness of the YAG layer is less than 1.0 nm, and preferably less than 0.5 nm.
[0046] The advantage of this implementation is that low surface roughness is important for minimizing the interface scattering of acoustic waves in layered SAW device structures. In addition, good surface roughness is a prerequisite for the wafer bonding process used in stacked manufacturing.
[0047] In an implementation of the method for producing a SAW resonator device according to the first aspect, the thickness of the YAG layer is in the range of 100 μm to 1000 μm.
[0048] The advantage of this implementation is that it can provide good mechanical support for the entire structure of the SAW resonator device.
[0049] Other applications and advantages of the embodiments of the present invention will become apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS
[0050] The accompanying drawings are intended to illustrate and explain different embodiments of the present invention, in which:
[0051] - Figure 1 A flow chart of a method for producing a SAW resonator device provided by an embodiment of the present invention is shown;
[0052] - Figure 2 Shown according to Figure 1 A cross-sectional view of a SAW resonator device produced by the flow chart;
[0053] - Figure 3 Shown according to Figure 1 Flowchart of the production of SAW resonator devices;
[0054] - Figure 4 A flow chart showing a method for producing a SAW resonator device provided by another embodiment of the present invention;
[0055] - Figure 5 Shown according to Figure 4 A cross-sectional view of a SAW resonator device produced by the flow chart;
[0056] - Figure 6 A flow chart showing a method for producing a SAW resonator device provided by another embodiment of the present invention;
[0057] - Figure 7 Shown according to Figure 6 A cross-sectional view of a SAW resonator device produced by the flow chart;
[0058] - Figure 8 The lay-up of the high speed layer and the passivation layer is shown. DETAILED DESCRIPTION
[0059] The disclosed scheme relates to a layered SAW resonator device using a Yttrium Aluminum Garnet (YAG) high phase velocity layer or substrate in the structure. Embodiments of the present invention are directed to a method for producing or manufacturing such a multilayer SAW resonator device. Therefore, Figure 1 A flow chart of a method for producing a SAW resonator device provided by an embodiment of the present invention is shown. Figure 2 Shown according to Figure 1 Flowchart of the cross-sectional view of the produced SAW resonator device.
[0060] refer to Figure 1 and Figure 2 The method 100 includes obtaining 110 a Yttrium Aluminum Garnet (YAG) layer 210. The method 100 also includes forming 120 an interdigital layer 220 on a top surface 212 of the YAG layer 210. The method 100 also includes forming 130 a piezoelectric layer 230 on a top surface 222 of the interdigital layer 220. The method 100 also includes applying 140 a conductive layer 240 on a top surface 232 of the piezoelectric layer 230 to form an interdigital transducer (IDT) 250 on the top surface 232 of the piezoelectric layer 230. The IDT 250 includes a first conductive electrode 252 connected to a first bus bar 254 and a second conductive electrode 256 connected to a second bus bar 258.
[0061] Figure 3 Shown according to Figure 1 1 is a flow chart of a SAW resonator device 100 produced in which the IDT 250 is shown in greater detail.
[0062] The first conductive electrodes 252 and the second conductive electrodes 256 are alternately arranged in the interdigital transducer 106. The IDT 106 is used to convert the electrical signal ES into an acoustic wave AW in the piezoelectric layer 230. The IDT 250 may include any number of first conductive electrodes 252 and any number of second conductive electrodes 256, for example, from a few conductive electrodes to thousands of conductive electrodes. In a symmetrical configuration, the number of first conductive electrodes 112 and second conductive electrodes 114 may be the same. The conductive electrodes and bus bars are naturally made of any suitable conductive material (for example, different metals). The conductive layer 240 forming the IDT 250 may include any suitable conductive material, for example: an aluminum layer, an aluminum-copper alloy layer, a copper layer, a copper-aluminum alloy layer, a chromium layer, a titanium layer, a tungsten layer, a gold layer, a palladium layer, and a molybdenum layer.
[0063] The phase velocity of the YAG layer 210 should generally be higher than the phase velocity of the piezoelectric layer 230 to achieve a waveguide effect and prevent acoustic loss from the resonator region (i.e., from the piezoelectric layer) into the substrate. Therefore, in an embodiment of the present invention, the piezoelectric layer 230 is any one of the following: a lithium tantalate layer, a lithium niobate layer, and an aluminum nitride layer.
[0064] We further recognize that some properties and structures of the YAG layer 210 have better effects than other properties and structures. Therefore, in an embodiment of the present invention, the YAG layer 210 may have any of the following: <111> Crystal orientation, <100> Crystal orientation, <110> Crystal orientation or polycrystalline structure. However, it is preferred <111> Crystal orientation, because its manufacturing process can minimize the number of defects associated with material growth. The surface roughness of the YAG layer 210 is also important, and the root mean square (RMS) surface roughness of the YAG layer 210 is less than 1.0nm, preferably, less than 0.5nm in an embodiment of the present invention. This surface roughness can minimize the interface scattering of acoustic waves and is a prerequisite for the wafer bonding process required to connect the layers of the stack to each other. The thickness d of the YAG layer 210 can be in the range of 100μm to 1000μm to ensure that sufficient mechanical support is provided to the layers above the YAG layer 210.
[0065] Additionally, the interleaved layers 220 used herein may include a silicon oxide layer. The purpose of the interleaved layers 220 is to provide effective temperature compensation for the SAW resonator device 100 and to serve as a wafer bonding layer between the layers above the YAG layer and the YAG layer. Changes in ambient temperature and operation at high input power affect the temperature of the SAW resonator device. Frequency stability varies with temperature and is described by the temperature coefficient of frequency (TCF). The temperature drift of the SAW resonator device 100 is related to the change in the stiffness coefficient of the piezoelectric material with temperature, but is also related to thermal expansion that affects both the size of the SAW resonator device 100 and the density of the piezoelectric material. Most materials become "softer" when exposed to increased temperatures, resulting in a decrease in the speed of the acoustic wave (i.e., the first-order TCF is negative), while other materials become "harder" and the speed increases with increasing temperature (i.e., the first-order TCF is positive). The TCF of LN, LT, and AlN is negative, while the TCF of silicon oxide is positive. By combining these materials and carefully choosing the dimensions of these materials, a SAW resonator device with zero TCF can be constructed.
[0066] According to embodiments of the present invention, there are two main methods of obtaining the YAG layer 210. In the first method, obtaining 110 the YAG layer 210 includes the steps of growing 112 a YAG crystal 216 and then wafering 114 the YAG crystal 216 to form the YAG layer 210. This is particularly interesting in the case where the YAG layer 210 has a certain thickness such that the YAG layer 210 can also form a substrate for the SAW resonator device 200.
[0067] The first method is described in detail below according to the following steps:
[0068] (1) Growing YAG crystal: To produce a YAG base substrate, it is necessary to grow a single crystal YAG crystal. Single crystal YAG crystal can be grown using the Czochralski method or a similar method. Controlling the crystal orientation of the YAG crystal is very important for minimizing the number of defects in the YAG crystal. The preferred crystal orientation is <111> , other crystal orientations can also be used according to performance requirements.
[0069] (2) Wafering process: Wafering is required to prepare the YAG base substrate of the present application. Among other things, the wafering process includes:
[0070] The YAG crystal is cut to produce wafer blanks, and chemical-mechanical polishing (CMP) is performed to obtain the required thickness and flatness of the wafer. The root mean square (RMS) surface roughness R of the YAG layer 210 is rms Should be less than
[0071] 1nm, that is, R rms <1nm, and preferably less than 0.5nm, that is, R rms <0.5. Each preparation step requires control of wafering parameters to ensure that the required specifications are met. For example, surface roughness can be measured by atomic force microscopy (AFM) or various optical interferometry techniques.
[0072] (3) In the next step, the interlaced layer 220 with a thickness ranging from several hundred nm to 1 um is deposited / grown. The interlaced layer 220 is used as a temperature compensation (TC) layer. The growth / deposition methods include, but are not limited to: Plasma-Enhanced Chemical Vapor Deposition (PECVD), reactive sputtering deposition, and pulsed laser deposition (PLD). Alternative methods include low-pressure CVD (LPCVD) and atomic layer deposition (ALD). The latter can produce films with excellent thickness uniformity, so no thickness trimming is required, but is limited by the low deposition rate.
[0073] (4) In this step, the interleaved layer 220 is deposited on the YAG layer 210 and the piezoelectric layer 230 .
[0074] (5) Optical measurement or other methods are required to measure the thickness and surface roughness of the deposited interleaved layer 220. CMP and thickness trimming are required to obtain uniform thickness (e.g., thickness tolerance <±2% relative to the nominal value) and low surface roughness (i.e., R rms <1nm). The steps of deposition / growth, metering, trimming and CMP can be repeated several times to achieve the desired surface roughness of the staggered layer 220. Low surface roughness is required to ensure high-quality bonding between the two layers. Examples of common staggered layer 220 materials include silicon dioxide (SiO2).
[0075] Therefore, in this case, the staggered layer 220 may have to be activated by an annealing process.
[0076] (6) In the next step, the piezoelectric layer 230 having the preferred crystal orientation is laminated and bonded to the YAG layer 210 and the interleaved layer 220.
[0077] 230 can be produced from a piezoelectric wafer by an ion implantation process. The thickness of the piezoelectric layer 230 is defined before bonding. The implanted ions create defects in the crystal structure along a plane that defines the boundary between the piezoelectric layer 230 and the donor wafer. The energy of the implanted ions defines the thickness of the piezoelectric layer 230. The target layer thickness can be <1um with a thickness tolerance of <±2% relative to the nominal value.
[0078] (7) After the ion implantation process, the piezoelectric layer 230 is bonded to the stack including the YAG layer 210 and the interleaved layer 220. The activation of one or both mating surfaces can be performed by a plasma process or a chemical treatment. To establish a molecular bond between the interleaved layer 220 and the piezoelectric layer 230, the mating surfaces can then be pressed together with considerable force. Thermal stress causes the bonded piezoelectric layer 230 to separate from the donor piezoelectric wafer along the defect plane created by the implanted ions.
[0079] (8) Perform metrology, such as optical measurement, to determine the thickness and surface roughness of the bonded piezoelectric layer 230.
[0080] (9) CMP and thickness trimming of the piezoelectric layer 230 are performed by scanning IBM or the like. The required surface roughness is R rms In the range of <1nm, that is, "SAW level".
[0081] (10) Forming an IDT topology on top of the composite substrate formed by the YAG layer 210, the interleaved layer 220 and the piezoelectric layer 230 includes IDT metal patterning. IDT topology formation methods may include lift-off lithography and metal evaporation. Metal deposition may also be achieved using sputtering techniques. Alternative methods for IDT topology formation include plasma, reactive ion or wet chemical etching to remove excess metal through a patterned photoresist or other masking material.
[0082] (11) Deposit a passivation layer (e.g., a composite film or a single layer with a thickness of <50 nm) by ALD or reactive sputtering deposition.
[0083] (12) Radio Frequency (RF) testing: RF testing of the SAW resonator device 100 is performed to determine its resonant frequency.
[0084] (13) The resonant frequency of the SAW resonator device 100 is adjusted by performing thickness trimming of the passivation layer by selective / partial etching (eg, scanning IBM) or by masking layer etching.
[0085] therefore, Figure 4 A flow chart showing a method for producing a SAW resonator device provided by another embodiment of the present invention is shown. Figure 5 Shown according to Figure 4 1. A cross-sectional view of a SAW resonator device produced by the flow chart in FIG. This is a second method for obtaining a 110YAG layer 210, that is, the YAG layer 210 is a YAG thin film layer. Therefore, the method 100 includes: forming a 160YAG layer 210 on the top surface 272 of the substrate 270. Steps 110 to 140 are combined with the previous Figure 1 The substrate 270 used herein is any suitable substrate, including, for example, any of the following: fused silica, quartz, and silicon.
[0086] The second method differs from the first method in the following steps:
[0087] (1) Obtain a YAG thin film layer 210, which is deposited on a substrate 270 by PLD or sputtering. The YAG thin film layer has any of the following: <111> , <100> or <110> Crystal orientation or polycrystalline structure.
[0088] (2) Perform thickness trimming and CMP of the YAG thin film layer 210 to obtain rms <1nm and preferably R rms The surface roughness is within the range of <0.5, and the thickness tolerance is <±2% relative to the nominal value.
[0089] Then, steps 3 to 13 of the first method described above are applied. The thickness of the YAG thin film layer 210 is in the range of 1 to 3 times the spacing p between the conductive electrodes 252, 256 of the IDT 250. The spacing p defines the resonant frequency of the SAW resonator device 200. The spacing p depends on the surface acoustic wave S propagating in the piezoelectric layer 230 during operation. A The phase velocity of the main mode.
[0090] therefore, Figure 6 A flow chart showing a method for producing a SAW resonator device provided by another embodiment of the present invention is shown. Figure 7 Shown according to Figure 6 1 . A cross-sectional view of a SAW resonator device produced by the flow chart in . In these embodiments, a high-speed dielectric layer is applied to the top surface 232 of the piezoelectric layer 230. Therefore, the method 100 includes: before applying 140 the conductive layer 240 to the top surface 232 of the piezoelectric layer 230, applying 132 a high-speed dielectric layer 260 to the top surface 232 of the piezoelectric layer 230. The method also includes: creating 134 an opening in the high-speed dielectric layer 260 to form an IDT 250 on the top surface 232 of the piezoelectric layer 230. Then, the method 100 continues with step 140, that is, applying the conductive layer 240 to the top surface 232 of the piezoelectric layer 230 as previously described. This scheme can achieve a piston operating mode of the multilayer surface acoustic wave resonator element, which is a prerequisite for successfully suppressing stray transverse modes.
[0091] Figure 8 The formation of a high velocity (HV) layer is shown in conjunction with the following steps:
[0092] (1) One or more high-speed dielectric layers 260 may be formed by depositing one or more high-speed dielectric material layers on the top surface of the piezoelectric layer 230. The high-speed dielectric layer 260 may include any of the following: silicon nitride, aluminum oxide, aluminum nitride, and beryllium oxide. The one or more high-speed dielectric layers may be deposited using conventional deposition techniques such as physical vapor deposition, chemical vapor deposition, or other methods.
[0093] (2) In order to remove one or more excess dielectric materials and make openings for subsequent formation of the conductor pattern of IDT 250, one or more photolithography processes can be used to produce openings similar to the conductor pattern in the photoresist or other masking material, exposing areas of one or more high-speed dielectric materials to be removed and protecting unmodified areas.
[0094] (3) Exposed areas of one or more high-speed dielectric materials may be removed by dry or wet etching techniques or other suitable methods.
[0095] (4) The method of forming the conductor pattern involves a lift-off process. The conductor pattern forming the IDT 250 of the SAW resonator device 100 can be produced on the top surface of the piezoelectric layer 230 by depositing one or more conductor layers in the openings of the high-speed dielectric material and the photoresist. Conductive metals such as aluminum, aluminum alloys, copper, and copper alloys can be used as the conductor layer. In addition, one or more other material layers can be arranged above and / or below the conductor layer, that is, between the piezoelectric layer 230 and the conductor layer / film. For example, the piezoelectric layer can be improved by a thin film of titanium, chromium, or other metal.
[0096] The conductivity of the first conductor pattern can be improved by forming a second conductor pattern made of a metal with higher conductivity, such as aluminum, copper, or gold, on portions of the first conductor pattern (eg, IDT bus bars and interconnections between IDTs).
[0097] (5) The photoresist may then be removed, thereby removing any excess material remaining on the conductor pattern.
[0098] In an embodiment of the present invention, a passivation layer may also be applied. The purpose of the passivation layer is to protect the SAW resonator device 100 from other processing steps (such as packaging and assembly). The passivation layer may be formed with a dielectric layer 290. Therefore, the method 100 may also include the following steps: forming 150 a dielectric layer 290 on the top surface 242 of the conductive layer 240; or forming 150 a dielectric layer 290 on the top surface 262 of the high-speed dielectric layer 260. The dielectric layer 290 may include any of the following: silicon nitride and silicon oxide. These materials are commonly available in manufacturing facilities, can be applied by a variety of methods, and have good mechanical and chemical stability.
[0099] Therefore, reference Figure 8 , the following steps can be layered onto the previously described steps 1 to 5:
[0100] (6) One or more passivation / tuning dielectric layers may be formed by depositing one or more dielectric material layers on top of the piezoelectric layer including the conductor pattern of the IDT. The one or more passivation / tuning dielectric layers may be deposited using conventional deposition techniques based on physical vapor deposition, chemical vapor deposition or other methods.
[0101] An optical measurement tool can be used to measure the thickness of one or more passivation / tuning dielectric layers. For example, the optical measurement tool can be an ellipsometer and / or a reflectometer. The measurement process is repeated to determine the thickness of one passivation / tuning dielectric layer at multiple measurement points on the top surface of the piezoelectric layer. The surface of the passivation / tuning dielectric layer can form a grid or matrix of multiple measurement points. A map of the passivation / tuning dielectric layer thickness can then be generated based on the measurement data.
[0102] Portions of the passivation / tuning dielectric layer may then be removed by a material removal tool, tuning the frequency of the SAW resonator device 200. For example, the material removal tool may be a scanning ion mill, a tool utilizing fluorine-based reactive ion etching, or some other suitable tool.
[0103] Finally, it should be understood that the present invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.
Claims
1. A method (100) for producing a surface acoustic wave (SAW) resonator device (200), characterized in that: The method (100) comprises: Obtaining a (110) yttrium aluminum garnet (YAG) layer (210); forming (120) an interlaced layer (220) on a top surface (212) of the YAG layer (210); forming (130) a piezoelectric layer (230) on a top surface (222) of the interlaced layer (220); A conductive layer (240) is applied (140) on a top surface (232) of the piezoelectric layer (230) to form an interdigital transducer (IDT) (250) on the top surface (232) of the piezoelectric layer (230), wherein the IDT (250) includes a first conductive electrode (252) connected to a first bus bar (254) and a second conductive electrode (256) connected to a second bus bar (258).
2. The method (100) according to claim 1, characterized in that: The phase velocity of the YAG layer (210) is higher than the phase velocity of the piezoelectric layer (230).
3. The method (100) according to claim 2, characterized in that: The piezoelectric layer (230) is any one of the following: a lithium tantalate layer, Lithium niobate layer and aluminum nitride layer.
4. The method (100) according to any one of the preceding claims, characterized in that The staggered layer (220) includes a silicon oxide layer.
5. The method (100) according to any one of the preceding claims, characterized in that The conductive layer (240) includes any one of the following: Aluminum layer, aluminum-copper alloy layer, copper layer, copper-aluminum alloy layer, chromium layer, titanium layer, tungsten layer, gold layer, palladium layer and molybdenum layer.
6. The method (100) according to any one of the preceding claims, characterized in that The method (100) comprises: before applying (140) the conductive layer (240) on the top surface (232) of the piezoelectric layer (230), Laying (132) a high-speed dielectric layer (260) on the top surface (232) of the piezoelectric layer (230); An opening is created (134) in the high speed dielectric layer (260) to form the IDT (250) on the top surface (232) of the piezoelectric layer (240).
7. The method (100) according to claim 6, characterized in that: The high-speed dielectric layer (260) includes any one of the following: silicon nitride, aluminum oxide, aluminum nitride and beryllium oxide.
8. The method (100) according to any one of the preceding claims, characterized in that The method (100) comprises: forming (150) a dielectric layer (290) on the top surface (242) of the conductive layer (240) and / or the top surface of the piezoelectric layer (230); or A dielectric layer (290) is formed (150) on a top surface (262) of the high-speed dielectric layer (260).
9. The method (100) according to claim 8, characterized in that: The dielectric layer (290) includes any one of the following: silicon nitride and silicon oxide.
10. The method (100) according to any one of the preceding claims, characterized in that The YAG layer (210) is a YAG thin film layer. The method (100) comprises: The YAG layer (210) is formed (160) on a top surface (272) of a substrate (270).
11. The method (100) according to claim 10, characterized in that: The thickness of the YAG layer (210) is in the range of 1 to 3 times the spacing (p) between the conductive electrodes (252, 256) of the IDT (250).
12. The method (100) according to claim 11, characterized in that: The spacing (p) defines the resonant frequency of the SAW resonator device (200), and the spacing (p) depends on the surface acoustic wave (S) propagating in the piezoelectric layer (230) during operation. A )’s phase velocity.
13. The method (100) according to any one of claims 10 to 12, characterized in that The substrate (270) includes any one of the following: fused silica, quartz and silicon.
14. The method (100) according to any one of the preceding claims, characterized in that The step of obtaining the (110) YAG layer (210) comprises: growing (112) YAG crystal (216); The YAG crystal (216) is wafered (114) to form the YAG layer (210).
15. The method (100) according to any one of the preceding claims, characterized in that The YAG layer (210) has any one of the following: <111> Crystal orientation, <100> Crystal orientation, <110> Crystal orientation or polycrystalline structure.
16. The method (100) according to any one of the preceding claims, characterized in that The root mean square (RMS) surface roughness of the YAG layer (210) is less than 1.0 nm, and preferably less than 0.5 nm.
17. The method (100) according to any one of the preceding claims, characterized in that The thickness (d) of the YAG layer (210) is in the range of 100 μm to 1000 μm.